(1→3)-α-D-Glucans from Aspergillus spp.: Structural Characterization and Biological Study on Their Carboxymethylated Derivatives

Alkali-soluble polysaccharides (ASPs) were isolated from the cell wall of four Aspergillus species (A. fumigatus, A. nidulans, A. niger, and A. wentii). The chemical and spectroscopic investigations (immunofluorescent labelling, composition analysis, methylation analysis, FTIR, and 1H NMR) indicated that the ASPs were polymers composed almost exclusively of (1→3)-linked α-D-glucose. After carboxymethylation (CM), the activity of (1→3)-α-D-glucans on three human cell lines (HSF, HeLa, and Jurkat) was assessed. Anti-proliferative, cytotoxic, and free radical scavenging action of CM-α-D-glucans was analysed. All the tested CM-α-D-glucans decreased cellular metabolism. However, incubation with CM-α-D-glucan from A. wentii and A. niger increased (by ca. 50%) the viability of HSF cells. Moreover, an over 5-fold increase in the viability was found for Jurkat cells incubated with CM-α-D-glucans from A. fumigatus and A. nidulans. The CM-(1→3)-α-D-glucans from the tested Aspergillus species expressed no free radical scavenging action. Fluorescent staining revealed that CM-α-D-glucans exerted slight toxic effects on cell viability and no action on F-actin filaments of cellular cytoskeleton organization.